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| United States Patent |
5,725,546
|
|
Samson
|
March 10, 1998
|
Detachable microcoil delivery catheter
Abstract
This invention is a surgical instrument, and specifically is a device for
delivering embolic coils to a selected site within the vasculature of a
human body. This instrument uses, and may include, the catheter used to
place the embolic coil. In particular, the device is made up of a pusher
wire having a distal tip which is configured to engage the proximal end of
an embolic coil. The device may also include a cylindrical pusher which
coaxially surrounds at least a portion of the pusher wire and cooperates
in the disengagement of the coil from the pusher wire and the ejection of
the vasoocclusive coil into the selected vascular site. The pusher wire's
engagement tip may be of any selected and convenient shape, and may be
grooved, if so desired, to enhance the engagement joint strength.
| Inventors:
|
Samson; Gene (Milpitas, CA)
|
| Assignee:
|
Target Therapeutics, Inc. (Fremont, CA)
|
| Appl. No.:
|
265580 |
| Filed:
|
June 24, 1994 |
| Current U.S. Class: |
606/191; 606/194 |
| Intern'l Class: |
A61M 029/20 |
| Field of Search: |
606/151,213,108,191
|
References Cited
U.S. Patent Documents
| 4643184 | Feb., 1987 | Mobin-Uddin.
| |
| 4739768 | Apr., 1988 | Engelson.
| |
| 4813934 | Mar., 1989 | Engelson et al.
| |
| 4884579 | Dec., 1989 | Engelson.
| |
| 4968296 | Nov., 1990 | Ritch et al.
| |
| 4994069 | Feb., 1991 | Ritchart et al.
| |
| 5098374 | Mar., 1992 | Othel-Jacobson et al.
| |
| 5108407 | Apr., 1992 | Geremia et al.
| |
| 5108420 | Apr., 1992 | Marks.
| |
| 5122136 | Jun., 1992 | Guglielmi et al.
| |
| 5180362 | Jan., 1993 | Worst.
| |
| 5217484 | Jun., 1993 | Marks.
| |
| 5234437 | Aug., 1993 | Sepetka.
| |
| 5250071 | Oct., 1993 | Palermo.
| |
| 5256146 | Oct., 1993 | Ensminger et al.
| |
| 5261916 | Nov., 1993 | Engelson.
| |
| 5263964 | Nov., 1993 | Purdy.
| |
| 5290295 | Mar., 1994 | Querals et al.
| |
| 5304195 | Apr., 1994 | Twyford, Jr. et al.
| |
Primary Examiner: Buiz; Michael
Assistant Examiner: Shai; Daphna
Attorney, Agent or Firm: Morrison & Foerster LPP
Claims
I claim as my invention:
1. A combination pusher-coil for occluding a vessel at a selected vascular
site within the vessel comprising:
(a) a helically wound coil having a proximal end and an opening in that
coil proximal end for accepting an engaging tip on a pusher wire, and
(b) a pusher wire having a longitudinal axis and a distal engaging tip,
said distal engaging tip having an outer surface with grooves formed
therein said outer surface is unitary with the distal engaging tip, said
distal engaging tip for entering the opening in the proximal end of the
helically wound coil.
2. The combination of claim 1 where the coil and the pusher wire are
engaged.
3. The combination of claim 2 further comprising a catheter body coaxial to
at least a portion of the pusher wire.
4. The combination of claim 1 additionally comprising a pusher tube coaxial
to the pusher wire and proximal to the distal pusher wire engaging tip for
pushing upon the proximal end of the helically wound coil.
5. The combination of claim 9 further comprising a catheter body coaxial to
at least a portion of the pusher wire.
6. The combination of claim 1 further comprising a catheter body coaxial to
at least a portion of the pusher wire.
Description
FIELD OF THE INVENTION
This invention is a surgical instrument, and specifically is a device for
delivering embolic coils to a selected site within the vasculature of a
human body. This instrument uses, and may include, the catheter used to
place the embolic coil. In particular, the device is made up of a pusher
wire having a distal tip which is configured to engage the proximal end of
an embolic coil. The device may also include a cylindrical pusher which
coaxially surrounds at least a portion of the pusher wire and cooperates
in the disengagement of the coil from the pusher wire and the ejection of
the vasoocclusive coil into the selected vascular site. The pusher wire's
engagement tip may be of any selected and convenient shape, and may be
grooved, if so desired, to enhance the engagement joint strength.
BACKGROUND OF THE INVENTION
The endovascular treatment of a variety of vascular maladies throughout the
body is an increasingly more important form of therapy. Catheters have
been used to place various treatment materials, devices, and drugs within
the arteries and veins of the human body. Examples of these devices and
their use in such treatments are shown in U.S. Pat. No. 4,994,069, to
Ritchart et al. Examples of vasoocclusive devices which are mechanically
detachable from installation devices provided within vascular catheters
include those found in U.S. Pat. No. 5,250,071, to Palermo, issued Oct. 5,
1993; in U.S. Pat. No. 5,261,916, to Engelson, issued Nov. 16, 1993; and
U.S. Pat. No. 5,304,195, to Twyford et al, issued Apr. 19, 1994. These
show methods and devices for delivery of coils or wires within the human
body to sites such as aneurysms, so to occlude those sites. The coils
delivered in such a manner may be of regular or helical configuration or
may assume a random convoluted configuration at the site. The coils
normally are made of a radiopaque, biocompatible materials such as
platinum, gold, tungsten, alloys of these materials, stainless steels,
various plastics, and the like.
In treating aneurysms, it is common to place a significant length of coil
within the aneurysm. The coils occlude the site by posing a physical
barrier to blood flow and by promoting thrombus formation at the site.
Coils have typically been placed at the desired site within the vasculature
using a catheter and a pusher. The site is first accessed by the
catheter--often with the help of a guidewire. In treating peripheral or
neural conditions requiring occlusion, the sites are accessed with
flexible, small diameter catheters such as those shown in U.S. Pat. Nos.
4,739,768 and 4,813,934. As noted above, the catheter may be guided to the
site through the use of guidewires such as those shown in U.S. Pat. No.
4,884,579 or by flow-directed means such as balloons placed integrally at
the distal end of the catheter. Use of guidewires involves the placement
of relatively long, torqueable proximal wire sections within the catheter
attached to more flexible distal end wire sections designed to be advanced
across sharp bends and vessel junctions. The guidewire may be visible
using fluoroscopy, particularly if it is encased in a radiopague material.
The radiopacity allows the attending physician to guide the catheter
through extremely tortuous vessels, even when surrounded by soft tissues
such as found in the liver or brain.
Once the site has been reached, the catheter lumen is cleared by removing
the guidewire (if a guidewire has been used) and the coils placed into the
proximal open end of the catheter and advanced through the catheter with a
pusher. Pushers may be guidewire-like devices having distal ends that are
adapted to engage and push the coils through the catheter lumen as the
pushers advance through the catheter. When the coil reaches the distal end
of the catheter, it is discharged from the catheter by the pusher at the
vascular site. This technique of discharging the coil from the distal end
of the catheter has a number of undesirable limitations. First, because of
the plunging action of the pusher and coil, the possibility of
miss-positioning the coil near the chosen site exists. Second, once the
coil has left the catheter, it may be difficult to reposition or to
retrieve the coil if such is necessary.
A number of techniques have been developed to enable accurate placement of
coils within a vessel. In one excellent technique found in U.S. Pat. No.
5,122,136 to Guglielmi et al., the coil is bonded via a metal-to-metal
joint to the distal end of a pusher. The pusher and coil are made of
dissimilar metals. The coil-carrying pusher is advanced through the
catheter to the selected site, and a low-voltage electrical current is
passed through the pusher coil assembly. The current causes the joint
between the pusher and the coil to be severed via electrolysis. The pusher
may then be retracted leaving the detached coil at a specific exact
position within the vessel.
Another technique involving mechanical detachment of embolic coils is found
in U.S. Pat. No. 5,261,916, to Engelson. In that patent, a coil having an
enlarged portion is mated with a pusher having a key way adapted to
receive that enlarged portion on the distal portion of the pusher. A
sleeve is used to hold the coil end member within the pusher key way. The
coaxial member is moved by sliding once the coil has reached the desired
site and the pusher with its key way is disengaged from the coil.
Another mechanical device is shown in U.S. Pat. No. 5,234,437, to Sepetka.
This patent shows the deployment of a vasoocclusive coil by the use of an
independently placed, threaded section mounted on the outside of the
pusher. The device meshes with the wires of the helical coil and may be
withdrawn either by simply pushing with a sleeve found without the pusher
wire or, presumably, by unscrewing the pusher from the distal end of the
coil. This disclosure does not suggest the use of an engageable distal tip
on the guidewire which is formed by grooves within the tip itself.
Another method of placing an embolic coil is shown in U.S. Pat. No.
5,108,407. The patent shows the use of a device in which embolic coils are
separated from the distal end of a catheter by the use of heat-releasable
adhesive bonds. Laser energy is transferred to a fiber optic cable to heat
the adhesive bond and sever the coil from the pusher wire.
There are a number of ways to place an implantable device within the human
body.
For instance, the concept of using a piece of hollow tubing to place a body
implant is well known. For instance, U.S. Pat. No. 4,643,184, to
Mobin-Uddin, shows an embolus trap for placement in the human body. The
device for deploying the embolus trap includes a guidewire and a
cylindrical capture cage which prevents the embolus trap from expanding
until it reaches an appropriate place within the vasculature.
Similarly, Ritch et al., U.S. Pat. No. 4,968,296, shows a device for
draining fluid from the eye so to treat glaucoma. Again, the drainage
implant is mounted on a wire. A hollow plunger is used to hold the implant
in position as the wire is withdrawn.
The Worst invention, U.S. Pat. No. 5,180,362, shows a drainage device
similar in concept to that shown in Ritch et al. above. A hollow needle
containing a coil-like drain is inserted into the eye, and the helix is
ejected using an ejector. The ejector is just said to be a rod. Engagement
of the coil is not mentioned in the patent.
The disclosure in Purdy, U.S. Pat. No. 5,263,964, shows a coiled attachment
apparatus in which a coil is attached to a guidewire or coil wire by glue,
solder, or some other means. A tubular sheath is passed over the
guidewire, and the coil is released by pulling on the guidewire while the
sheath bears against the coil.
None of these disclosed devices suggests the use of a pusher wire which is
simply press-fit into the proximal end of the vasoocclusive coil. Nor do
any of these disclosures show a pusher having serrations or grooves in the
tip of the pusher wire itself.
SUMMARY OF THE INVENTION
This invention is a device for placing coils within the vasculature of a
mammalian body so as to occlude the selected site. The device includes a
pusher having a distal engaging tip and a coil having an open proximal end
which may be engaged by that tip. The pusher preferably is a guidewire
having a ground conical distal tip which may further have circumferential
or helical grooves in that conical region. The grooves and the conical tip
are used to engage the interior of the vasoocclusive coil and hold it
during axial traversal of the catheter. The engaging tip holds the
vasoocclusive coil with such strength that it may be moved axially in
either direction in a catheter without fear of loss. The engaging tip may
be cylindrical in form and, again, may have either helical grooves or
circumferential grooves in the cylindrical area (which is to fit inside
the proximal end of the vasoocclusive coil) so to hold the vasoocclusive
device as it is moved axially through the catheter or vasculature.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows, in high magnification, a side view, cross section of a
generic device made according to the invention.
FIGS. 2 and 3 show magnified side views of two conical pusher wire tips
made according to this invention.
FIGS. 4, 5, and 6 show highly magnified inside views of cylindrical
engaging tips made according to the invention.
DESCRIPTION OF THE INVENTION
FIG. 1 shows an overall assembly (100) of components which make up a broad
variation of the invention. In particular, a helical coil (102) is shown
as the vasoocclusive device. The proximal end (104) of the vasoocclusive
coil (102) is open and adapted to receive and engage the engageable tip
(106) found on pusher core wire (108). Engageable tip (106) is shown in
this drawing to be conical and to have an axis which runs generally in
coincidence with the axis of the pusher wire (108). As will be described
below in more detail, the engageable tip (106) may be grooved or may be
left to be smoothed or may be left in a semi-machined or sanded condition
to achieve good adherence to the interior of coil (102) upon insertion.
The engageable tip (106) is to enter the open end of coil (102). The coil
will typically have an open lumen for a significant distance from its
proximal end (104).
The coil itself should be of a size sufficiently small that it may be
advanced through a catheter (110) and desirably is about the same diameter
as cylindrical pusher (112). The coil should also be appropriately sized
for accessing the targeted vascular site. For instance, when accessing a
brain aneurysm in a small vessel, an appropriately sized catheter is
usually quite small and very flexible. The coil in such a situation must
be sufficiently small to fit through the catheter and pass out the distal
end of the catheter at the treatment site.
The coil is desirably made up of radiopaque, physiologically compatible
material. The material may be platinum, gold, tungsten, alloys of these
metals, or stainless steel or various polymers. These polymers may be used
either as coil material per se or in conjunction with metallic markers so
to provide sufficient radiopacity.
The size of the coil in its constituent windings will depend upon the use
to which the coil will be put. For occluding peripheral or neural sites,
the coils will typically be on the smaller side, e.g., of 0.05 to 0.15"
diameter wire (platinum or platinum/tungsten alloy) that is wound to have
an inner diameter of 0.15 to 1.5" with a minimum pitch. By "minimum pitch"
we mean to say that the pitch is equal to the diameter of the wire used in
the coil. The length of such coils would normally be in the range of 0.5
to 100 cm, preferably 0.5 to 40 cm. If desired, the coil may be formed in
such a way that the coil is essentially linear as it passes through the
catheter and yet assumes a randomly oriented condition once it is released
from the distal end of the catheter. A discussion of this variation may be
found in U.S. Pat. No. 4,994,069, to Ritchart et al., the entirety of
which is incorporated by notice.
It is also within the purview of this invention that filamentary braids,
tassels, or looping ties be placed on the exterior surface of the coils.
These filamentary materials improve the ability of the coil to form a
thrombus at the elected site.
Further shown in FIG. 1 is a catheter body (110) and coaxial tubular pusher
(112). Finally a radiopaque band (114) is also depicted in the figure.
The device shown in FIG. 1 is shown as it would be seen by a person either
loading the coil (102) onto engageable tip (106) of pusher wire (108) or,
conversely, just after the coil has been cut loose. As is described in
many of the patents discussed above, a good way to utilize this device is
to load the coil (102) onto distal end (106) of pusher wire (108) and
retract the coil (102) within the lumen of catheter (110). Obviously
pusher (112) is also retracted within the catheter body (110).
The device may be employed by using known techniques for placement of
catheters. For instance, catheter (110) may be put in place by use of a
guidewire, the guidewire then being withdrawn, and the coil (102)
introduced into the catheter (110) lumen followed by a pusher wire (106)
and pusher tubing (112). Once the coil is carefully placed at the desired
site, a variety of ways of using the device may then be utilized. For
instance, pusher core wire (108) may be "unscrewed" from the interior of
coil (102). The pusher tubing (112) may be used in this instance to
prevent the rotation of the coil (102) as pusher (108) is screwed and
withdrawn from the catheter body.
FIG. 2 shows a variation of the distal tip of pusher wire (116) in which
the engaging end includes helically placed grooves (118) on that engaging
section. Desirably the spacing of these grooves (118) is such that it
matches the pitch of the vasoocclusive coil (102 in FIG. 1) and thereby
increases the holding capacity of the resulting joint.
It may be apparent that the overall diameter of the vasoocclusive coil
(102) as it engages the distal tip of the pusher wires is slightly
increased. The amount of increase must be balanced in such a fashion that
it does not bind with the interior diameter of the catheter in order to
fulfill the major goal of the inventive device. That is to say, when the
pusher core wire is locked to the vasoocclusive coil (102) without
excessively expanding the diameter of a vasoocclusive coil (102), the
device operates quite well in that it does not cause kinking of the
catheter as it is traversed through the catheter's lumen. Consequently,
some thought must be had in choosing the size and slope of the conical
engaging end.
FIG. 3 shows a conical engaging end (120) also having helical grooves in
the cone face. This variation, however, has shoulder (122) at the base of
the cone. This shoulder should allow the vasoocclusive coil (102) to mesh
with cone (120) without excessive splaying of the coil. It is a way to
control the increase of a radius which occurs when the engageable end
(116) is engaged in the proximal end of the vasoocclusive coil.
It should be apparent that the variations of the conical engaging end shown
in FIGS. 1, 2, and 3 may utilize grooves placed in the conical face which
are merely concentric and not helical in form. The engageability of this
variation is not quite as good as with the helical grooves portrayed in
the figures, but certainly they are acceptable and somewhat easier to
place on the distal end of the pusher wire.
FIG. 4 shows still another variation of the pusher wire in side view.
Located on the distal tip is a generally cylindrical engagement end (124)
having a rounded tip (126). As an aside, the conical tips described above
may also have a rounded tip such as (126) found in this drawing. In any
event, the diameter of cylindrical engaging tip (124) is slightly larger
than the lumen of the coil used as the vasoocclusive device (e.g., 102 and
FIG. 1). The concept here is that when the coil is pushed over the
receiver end, there should be a slight compression fit.
FIG. 5 shows a cylindrical engaging end (128) similar to that seen in FIG.
4 but in which the engaging end has circumferential grooves (130) so to
cooperate with the terms of the helical coil and provide a bit higher
measure of locking with the engaging end (128).
Similarly, FIG. 6 shows another variation of the cylindrical engaging tip
(132) having a helical thread (134) cut or otherwise placed into the tip
so to engage the vasoocclusive helically wound coil with even greater
tenacity. Again, the outer diameter of the vasoocclusive coil as it
nestles up against shoulder (136) should not exceed the diameter of the
pusher wire at that point. In this way, a smooth transition is had and it
is less likely to cause kinking or other problems within the delivery
catheter.
Although the discussion of this invention has, in general, emphasized the
structure at the distal portion of the pusher wire and the proximal end of
the vasoocclusive device, it should be emphasized that the invention is
not so limited. The catheter and pusher must be of such a length that they
are capable of being advanced through the vasculature to the target site
without a problem. The pusher wire and tubular pusher shown above in FIG.
1 must be of a length sufficient to push the coil to be delivered
completely through the catheter and, indeed, typically out of the other
end into the region of the site where the occlusion is to be created so
that the pusher can then be disengaged and the pusher and catheter
assembly removed without significant movement of the vasoocclusive coil.
Modifications of the device described above and methods of using it in
keeping with this invention that are apparent to those having ordinary
skill in this mechanical and surgical instrument design art and related
fields are intended to be within the scope of the claims which follow.
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